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Name Reactions
Published in Benny K.G. Theng, Clay Mineral Catalysis of Organic Reactions, 2018
We should also mention that layer silicates other than montmorillonites can catalyze or act as a support for reagents that can promote the Knoevenagel condensation reaction. Martín-Aranda et al. (2005), for example, reported that Li+- and Cs+-exchanged saponites could promote the condensation of benzaldehyde (1) with malononitrile (2) under ultrasonic irradiation to afford the corresponding α,β-unsaturated benzylidene malononitrile (3), according to Scheme 5.17. Similar condensation reactions can be catalyzed by kaolinite (Heravi et al. 2009) as well as by zirconium oxide nanoparticles, deposited on the external surface of sepiolite fibers (Letaïef et al. 2011). More recently, Sadjadi et al. (2017) used dodecatungstophosphoric acid, supported on silylated halloysite nanotubes, to promote the synthesis of pyrazolopyranopyrimidine derivatives via the four-component domino reaction of barbituric acid, hydrazine hydrate, ethyl acetoacetate, and benzaldehyde, involving a Knoevenagel condensation step.
Polymers
Published in Bryan Ellis, Ray Smith, Polymers, 2008
Polymer Solutions Dilute: Theta temps. for various solvents have been reported [5,104] 9 -49° (isoamyl acetate), -9° (n-butyl formate), 34-35° (cyclohexane), 20-154.2° (cyclopentane), 22° (bis(2-ethylhexyl)phthalate), -44-139° (EtOAc), 70° (ethyl cyclohexane), 60-70.5° (methyl cyclohexane), 28.0-30.6° (1-phenyl- decane), -80-178° (n-propyl acetate), -46° (isobutyl acetate), 6° (1- chlorodecane), 58.6° (1-chlorododecane), 79-87.8° (cyclohexa- nol), 31 -35.9° (diethyl malonate), 51.5-59.6° (diethyl oxalate), 108.5° (ethyl acetoacetate),43-114° (methyl acetate), 8.0° (3- methyl cyclohexanol), -27 -107° (isopropyl acetate). Theta temps. have also been reported for solvent mixtures [5,104]. The different concentration regimes for rheology have been reported for different MWs [2,106]. The intrinsic viscosity of dilute solns. is relatively insensitive to temp. over the usual measurement range (25 -55°) [2,107] and depends on the value of MW and also the solvent quality [108]. The effect of MWon intrinsic viscosity in toluene (10% w/w, ASTM D445) has been investigated [109]. Various values for the Mark-Houwink equation parameters have been reported for different solvents [5,105,108,110] Polymer Solutions Concentrated : For more conc. polymer solns., the zero shear viscosity depends on both the concentration and the average MW [106,111]. This relationship has been investigated for polystyrene solns. in toluene and trans-decalin at 25° and n- butylbenzene at 30° [112]. The zero shear viscosity at polymer concentrations of 50-100% (w/w) and 60-225° in ethylbenzene have been studied [113]
Biomarkers of exposure and effect in a working population exposed to lead, manganese and arsenic
Published in Journal of Toxicology and Environmental Health, Part A, 2018
Daniela C Serrazina, Vanda Lopes De Andrade, Madalena Cota, Maria Luísa Mateus, Michael Aschner, Ana Paula Marreilha dos Santos
Triton X-1000, nitric acid ≥65% (HNO3), diethyl ether ≥99.8% (C4H10O), acetylthiocholine iodide (C7H16INOS) ≥98%, 5-aminolevulinic acid hydrochloride (C5H9NO3.HCL) 98%, ethopropazine hydrochloride ≥98% (C19H24N2S HCl) and 5,5´-Dithiobis(2-nitrobenzoic acid) ≥98% (C14H8N2O8S2) purchased from Sigma; ethyl acetoacetate (C6H1003) ≥98% and ethanol absolute p.a. (C2H5OH), purity (GC) ≥99% obtained from Merck; ethyl acetate 99% (C4H8O2), nitric acid trace metal grade (HNO3) 67–69% assay and hydrogen peroxide 30% W/V (H2O2) obtained from Fisher Chemical; hydrochloric acid 36.5–38.0% ACS Basic (HCL) from Scharlab; glacial acetic acid 99.7% (CH3COOH) from Panreac; MRC TM 24.3 (Environment Canada analytical reference material, Pb, As, and Mn, included in the composition); manganese standard for AAS Analytical, purchased from Fluka.; lead and arsenic for AAS standard solution TraceCERT®, from Sigma.
Fe3O4@SiO2@ADMPT/H6P2W18O62: a novel Wells–Dawson heteropolyacid-based magnetic inorganic–organic nanohybrid material as potent Lewis acid catalyst for the efficient synthesis of 1,4-dihydopyridines
Published in Green Chemistry Letters and Reviews, 2018
Mohammad Ghanbari, Sanaz Moradi, Moslem Setoodehkhah
A tentative mechanism for the synthesis of 1,4-DHPs catalyzed by Fe3O4@SiO2@ADMPT/H6P2W18O62 nanocatalyst is proposed in Scheme 5. In step I, the ammonium acetate was converted to the ammonia and acetic acid. Then, the ammonia as a base was produced the 4-ethoxy-4-hydroxybut-3-en-2-one (A). In step II, the formation of product B as an intermediate can be performed via the standard Knoevenagel condensation by the nucleophilic addition of A component to the carbonyl group of the aldehyde which was activated by the Fe3O4@SiO2@ADMPT/H6P2W18O62 nanocatalyst. Another key intermediate is ester enamine C, produced by condensation of ammonia with the second equivalent of the ethyl acetoacetate which was activated by the Fe3O4@SiO2@ADMPT/H6P2W18O62 nanocatalyst. In step III, the A and B intermediates were reacted via Michael addition to afford the intermediate D. Finally, Intramolecular cyclization of enamine D by the nucleophilic addition of enamine to the carbonyl group which was activated by the nanocatalyst was produced the target product 1,4-DHP 4a.
Coumarin dimers of benzidine and phenylenediamine cores: synthesis, characterisation and mesomorphic properties
Published in Liquid Crystals, 2020
Abdulkarim-Talaq Mohammad, Mohammad Hameed Al-Mohammedi, Mohammed Zghair Ghdhayeb, Suaad Mohammed Husain Al-Majidi
Compound 1 was prepared by Knoevenagel condensation reaction of an equimolar mixture of 2,4-dihydroxybenzaldehyde (2.08 g, 15 mmol) and ethyl acetoacetate (1.95 g, 15 mmol) in 40 ml absolute ethanol in the presence of few drops of piperidine as catalyst. The reaction mixture was refluxed for 2 h, cooled and poured into ice-cold dilute hydrochloric acid, and then filtered the precipitate. The precipitate was washed with water and recrystallised from ethanol yielded pale yellow crystals. Compounds 2a-i was prepared according to the previous work and its esterification with 1 gives compounds 3a-i [30,38].